Incendiary projectile



Jan. 14, 1969 CUsTARD 3,421,439

INCENDIARY PROJECTILE Filed Sept. 29, 1961 IN VEN TOR. GEORGE H. CUSTARD 7- QW- MMM? 'ATTORNEYS United States Patent 1 Claim This invention relates to a projectile and has for an object to provide one of enhanced incendiary effect. Another object is to provide a projectile which may be an incendiary yet capacle of being designed for higher or lower muzzle velocities without substantial change in the weight of the explosive carried thereby and without substantial change in weight of the propelling charge for said projecticle.

A substantial change in deviation of burst by pyrophoric particles was effected by the invention of Thomas Stevenson, US. Patent 2,951,752 dated Sept. 6, 1960, for Incendiary Composition. Prolonged burning has long been an object sought for incendiary projectiles. The present invention, while not confined to projectiles carrying incendiary loads, is nevertheless useful in providing an improved incendiary effect.

Specifically this is attained by providing a shell body which is ignited by a high explosive creating a high enough temperature estimated to be about 3600 K. (absolute) igniting the inner wall surfaces of said projectile body when ignited before or when the body is shattered.

Referring to the drawing:

The single figure shows a longitudinal section through a 20 millimeter projectile of a high explosive incendiary type with the usual nose fuze carrying a detonator as the impact initiator therefor.

A prior construction included a nose cone 9 containing a primer and initiator, not shown, and forming no part of this invention. A booster charge 12 was responsive to ignition by the detonator explosion, and a high explosive in 3 parts is shown at 13a, 13b and 130. These parts represent approximate increments used in loading into the projectile body. The usual rotating band 11 gave the 20 millimeter projectile the stabilizing spin desired. The body of that prior projectile was of steel.

According to the present invention that body 10 is now constituted of zirconium, or titanium, without changing the charge carried within the body.

In operation the primer ignited the booster charge 12 on inpact with a target, igniting the high explosive known to the art as -MOX-2B. This high explosive incendiary has the following composition in weight:

Percent Ammonium perchlorate 35 Aluminum, atomized 52 Cyclotrimethylene trinitramine (RDX) wax 6 Calcium stearate 2 Graphite 1 (TNT) trinitrotoluol 4 It is believed the high explosive developed a temperature of about 3600 K. (absolute) within the shell body 10. In a few milliseconds it ignited the inner wall surfaces of said body before or during rupture and as the body instead of being of steel, was now of one of the two metal fuels mentioned above, namely of zirconium, or titanium or some metal fuel alloy of these. The body fragments are larger and heavier than the usual metal fuel compositions heretofore used .in incendiary projectiles. Being heavier they travel farthest from the immediate area of burst and penetrate the target thereby inflicting incendiary damage to a greater depth. Although it has not been possible to make as close a study of what happens inside such a 20 millimeter projecti-cile at and just before burst, nevertheless indications point to the probability the inner wall surface of the projectile body of this invention ignites by the high heat of ignition of the high explosive just before or just after the actual burst occurs. The foremost essentials of an incendiary possessing the advantages of this invention are the body of the metal fuels named and a high temperature explosive giving off the intense heat needed to ignite the body fragments.

A special advantage of the metal. bodies named, is their ballistic flexibility to suit the needs of special situations. The titanium body enables a higher muzzle velocity to be obtained with the same size and design of shell. This is also true of zirconium because the density of these metals is lower than the density of steel.

The booster charge 12 may be some one of those commonly used such as TNT (trinitrotoluol), or tetryl, or RDX (cyclotrimethylene trinitramine). The explosive charge increments are also compressed under about] 30,000 pounds per square inch pressure. Any good high explosive capable of raising the inner wall surface of the projectile body to its kindling temperature may be used. The booster is a 20 millimeter projectile may be about 30 grains and the main body charge about grains.

Under this invention inner surface portions of a projectile body when made of zirconium or titanium become ignited and may burn for as long a time as about one minute. The explosive tetryl is Well known and according to the 30th edition of the Handbook of Chemistry and Physics (1947) is an N-methyl-N-ZA,6-tetranitroaniline; or methylpicrylnitramine, having the formula (NOZ)3CGH2N (NOZ)CH3- I claim:

1. An incendiary projectile of 20 millimeter size having a hollow body containing an impact responsive primer in a nose of said projectile body, a booster charge adjacent said primer and of an explosive selected from the class consisting of tetryl, TNT, and RDX, and a main charge adjacent the booster of approximately 100 grams of an explosive capable of raising the temperature on the inner surface of said body to about 3000 to 3600 K. when said body is of a metal selected from the group consisting of zirconium and titanium, said main charge being an explosive having the composition consisting of about the following materials by weight: ammonium perchlorate 35%, aluminum atomized 52%, cyclotrimethylene trinitramine wax 6%, calcium stearate 2%, graphite 1%, trinitrotoluol 4%, whereby on explosion and fragmentation portions of the body become ignited and may burn for as long a time as about 1 minute.

References Cited UNITED STATES PATENTS 1,878,491 9/1932 Goss.

2,323,303 7/1943 Bluehdorn et al 102-90 2,586,801 2/ 1952 Epler et al. 102-90 X 2,775,938 1/1957 Wave 102-90 X 2,780,995 2/1957 Migliaccio 102-90 X 2,791,178 5/1957 Thompson 102-90 X 2,801,590 8/1957 Balke et a1 102-90 2,992,086 7/ 1961 Porter 149-38 X ROBERT F. STAHL, Primary Examiner. 

1. AN INCENDIARY PROJECTILE OF 20 MILLIMETER SIZE HAVING A HOLLOW BODY CONTAINING AN IMPACT RESPONSIVE PRIMER IN A NOSE OF SAID PROJECTILE BODY, A BOOSTER CHARGE ADJACENT SAID PRIMER AND OF AN EXPLOSIVE SELECTED FROM THE CLASS CONSISTING OF TETRYL, TNT, AND RDX, AND A MAIN CHARGE ADJACENT THE BOOSTER OF APPORXIMATELY 100 GRAMS OF AN EXPLOSIVE CAPABLE OF RAISING THE TEMPERATURE ON THE INNER SURFACE OF SAID BODY TO ABOUT 300* TO 3600*K. WHEN SAID BODY IS OF A METAL SELECTED FROM THE GROUP CONSISTING OF ZIRCONIUM AND TITANIUM SAID MAIN CHARGE BEING AN EXPLOSIVE HAVING THE COMPOSITION CONSISTING OF ABOUT THE FOLLOWING MATERIALS BY WEIGHT: AMMONIUM PERCHLORATE 35% ALUMINUM ATOMIZED 52%, CYCLOTRIMETHYLENE TRINITRAMINE WAX 6% CALCIUM STEARATE 2%, GRAPHITE 1%, TRINITROTOLUOL 4%, WHEREBY ON EXPLOSION AND FRAGMENTATION PORTIONS OF THE BODY BECOME IGNITED AND MAY BURN FOR AS LONG A TIME AS ABOUT 1 MINUTE. 